### Author Topic: Coordinate System Inquiry  (Read 169 times)

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#### wizman

• Newt
• Posts: 196
##### Coordinate System Inquiry
« on: October 25, 2017, 12:40:41 pm »
Hi,

I would request for help regarding coordinate system.  The vertical datum of WGS84 is EGM96. I would like to inquire if what is the vertical datum of ain el abd?

Thank you.

Ron

#### mjfarrell

• Seagull
• Posts: 14101
• Every Student their own Lesson
##### Re: Coordinate System Inquiry
« Reply #1 on: October 26, 2017, 08:38:07 am »

Michael Farrell
http://primeservicesglobal.com/

#### mjfarrell

• Seagull
• Posts: 14101
• Every Student their own Lesson
##### Re: Coordinate System Inquiry
« Reply #2 on: October 26, 2017, 09:03:15 am »
and look at the following:

https://epsg.io/20439

Michael Farrell
http://primeservicesglobal.com/

#### Pointdump

• Mosquito
• Posts: 19
##### Re: Coordinate System Inquiry
« Reply #3 on: October 28, 2017, 06:13:27 am »
Hi Ron,

WGS84 does not have a Vertical Datum. What it has is an Ellipsoid, which is a mathmatical representation of Mean Sea Level. EGM96 is a Geoid, which is a measured, lumpy, irregular surface that aims to accurately represent Gravitational Equipotential. The difference between the WGS84 Ellipsoid and EGM96 is called the Geoid Height. Ain el Abd Coordinate System (EPSG:4204) is based on the International 1924 Ellipsoid.

To answer your question of "what is the vertical datum of ain el abd?", it is whatever Geoid Model you choose to more accurately represent your surface elevations.

Dave

#### wizman

• Newt
• Posts: 196
##### Re: Coordinate System Inquiry
« Reply #4 on: October 29, 2017, 08:48:32 am »
Thank you mjfarrell and Pointdump for your replies.  Sorry for the late reply, I just saw your messages.  I thought i should be getting notification since i started this thread.  Vovka also pointed me to a link which says KSA has two geoid models.  I'll read through your posts and come back if i have any other questions.

Thanks,
Ron